This invention relates to an apparatus for and a method of cleaning a photo-sensitive body and, more particularly, to an apparatus for and a method of cleaning a photo-sensitive body in a copying machine by removing the residual toner on the surface of a photo-sensitive body with a cleaning blade after completion of the image transfer onto a copying sheet.
Hitherto, efforts have been made to improve the operability and the maintainability of copying machines. Particularly, up to date there is a strong demand for miniaturizing and reducing costs of the copying machine. In order to meet this demand for miniatuarization and cost reduction, it has been proposed to use a platelike cleaning blade for a photo-sensitive material coated drum cleaning apparatus which serves to remove the residual toner remaining on a surface of the photo-sensitive material coated drum after completion of the image transfer operation.
In such a drum cleaning apparatus in which the cleaning blade is used, where the cleaning blade is at all times held in forced contact with the photo-sensitive body surface, the crystal structure of the photo-sensitive material is changed in quality to cause deterioration of the copied image. For the purpose of preventing this deterioration, various improvements have been proposed. For example, there has been proposed and widely accepted a two-position drive mechanism, in which, as shown in FIG. 1, a cleaning blade 11 is held spaced apart from the surface of the photo-sensitive material coated drum 10 when it is out of operation and, as shown in FIG. 2, is brought into forced contact with the surface of the drum 10 at the time of the commencement of the cleaning operation.
Further, in the light of the afore-mentioned demand for miniatuarization and cost reduction it has been proposed and widely accepted that a common drive source is used for either of the two-position drive mechanism for the cleaning blade 11 and a drive mechanism for the drum 10.
In this case, the cleaning blade 11 is instantaneously brought from its position spaced apart from the surface of the drum 10 into forced contact therewith at the time of commencement of rotation of the drum 10. Therefore, the cleaning blade 11 that strikes the surface of the drum 10 has a great impact. Particularly, the tip of the cleaning blade 11 is given with an extremely great impact at the moment when the tip strikes the drum surface, since the area of contact therebetween is narrow. Consequently, the tip of the cleaning blade 11 is likely to be turned up in the direction of rotation of the drum 10 or suffer other damages. When the cleaning blade 11 is thus damaged, it can no longer completely remove the residual toner on the drum surface. This causes the occurrence of what is called "the film-forming" phenomena, that is, the formation of a toner film on the drum surface.
When such a toner film is formed, as one problem, the image forming function of the relevant area of the drum 10 is reduced resulting in the deterioration of the image quality.
As another problem, since the drum 10 and cleaning blade 11 are driven by the common drive source, the drum 10 commences its rotation simultaneously with the commencement of the movement of the cleaning blade 11 from the position spaced apart from the surface of the drum 10 to the position at which the cleaning blade 11 is in forced contact with the drum 10. Therefore, some of the toner 12 on the drum surface has not been removed by the cleaning blade 11, as shown in FIG. 2, since the drum surface portion bearing such some toner is passed by under the same, before the cleaning blade 11 is brought into forced contact with the drum sruface. This toner 12 which is not removed is likely to fall from the drum surface or be scattered in the copying machine during the subsequent rotation of the drum 10. The falling or scattered toner contaminates internal component parts of the copying machine. Particularly, if the charger is contaminated, the image forming function becomes inferior.
To solve the afore-mentioned first problem, i.e., the damage of the cleaning blade 11, it may be thought to bring the cleaning blade 11 into forced contact with the drum 10 prior to the commencement of rotation of drum 10. However, even by so doing there is still a coefficient of static friction between the tip of the cleaning blade 11 which is already in contact with the drum surface at the time of commencement of rotation of the drum 10 and the surface thereof, so that the tip of the cleaning blade in contact with the drum experiences a considerable load. In other words, this arrangement cannot completely solve the problem that the tip of the cleaning blade 11 is liable to damage.
To solve the second problem, i.e., the falling or scattering of the toner left without being removed, it has been contemplated to drive the cleaning blade 11 independently by a separate drive source, for instance one using a solenoid, prior to the commencement of driving of the drum 10 with sacrifice in size. In this case, however, about 20 W of power has to be supplied to the solenoid for effectively bringing the tip of the cleaning blade 11 into forced contact with the drum 10. Therefore, the use of the solenoid as the drive source for the cleaning blade 11 does not only increase power consumption, which is undesired from the standpoint of economy, but also gives rise to other problems such as the necessity of separately providing a means for radiating heat generated in the solenoid.